Abstract: :
Purpose: Lumican is a small leucine-rich repeat proteoglycan(SLRP) found in various collagenous connective tissues suchas cornea. Lumican and other SLRPs are thought to bind collagenand have been implicated in the regulation of collagen fibrildiameter and arrangement in collagenous matrices. Our currentresearch focuses on ascertaining the collagenous architectureof wild-type and transgenic neonatal mouse corneal stroma before,during, and after eye-opening.Methods: Corneas from youngwild-type and lumican-null mice (neonatal days 8, 12, and 14)were excised and immediately immersed in fixative. Specimenswere subsequently studied by synchotron x-ray diffraction toobtain information regarding the average spacing of collagenfibrils in the tissues.Results: Average interfibrillar Braggspacing in the corneas of 8 day-old wild-type mice (n=6) werejust below the value of 48nm found previously in the corneasof 6 month-old wild-type mice when examined in this manner.In two of three 12 day-old corneas, collagen spacing was elevated.At post-natal day 14, three of the four corneas examined hadaverage interfibrillar spacings below 45nm. It was establishedthat collagen interfibrillar Bragg spacing in the corneas of8 day-old mice homozygous for a null mutation in lumican (n=6)were consistently higher than in the corneas of their age-matchedcounterparts.Conclusions: Recent work with neonatal mice hasindicated that the cornea is thicker just before eye-opening(day 12) than at times just before and after this period. Ourdata suggests that, in most cases, this may be due to an increasein the average collagen interfibrillar distance. The findingthat average collagen interfibrillar spacings were consistentlyhigher in the corneas of lumican deficient mice than they wereat this time in the corneas of wild-type mice is supportiveof a structural role for lumican early in corneal stromal development.